cranks but won't start issue
 

I have a vehicle that cranks but won't start (1986 Vanagon with the VW DigiFunky EFI system)

The battery reads 13 V just sitting (but it is on a float (trickle) charger).

When I crank it, the battery voltage drops to a bit less than 11 V (about 10.8 or so).

When I stop cranking it, it slowly builds up past 12.4 V (from the trickle charger it is on).

Can I rule out the battery as a cause of the Van not starting based on the above?

Unhook the charger while cranking. Battery seems ok.

Air, spark, fuel.
Make sure the throttle flap is opening and smell the tailpipe.
If it smells like gas, spark is the only thing left.